Synthesis and characterization of poly(n-butyl methacrylate)-b-polystyrene diblock copolymers by atom transfer radical emulsion polymerization

Poly(n-butyl methacrylate) (PBMA)-b-polystyrene (PSt) diblock copolymers were synthesized by emulsion atom transfer radical polymerization (ATRP). PBMA macroinitiators that contained alkyl bromide end groups were obtained by the emulsion ATRP of n-butyl methacrylate with BrCH3CHCOOC2H5 as the initiator; these were used to initiate the ATRP of styrene (St). The latter procedure was carried out at 85 degrees\C with CuCl/4,4'-di(5-nonyl)2,2'-bipyridine as the catalyst and polyoxyethylene(23) lauryl ether as the surfactant. With this technique, PBMA-b-PSt diblock copolymers were synthesized. The polymerization was nearly controlled; the ATRP of St from the macroinitiators showed linear increases in number-average molecular weight with conversion. The block copolymers were characterized with IR spectroscopy, H-1-NMR, and differential scanning calorimetry. The effects of the molecular weight of the macroinitiators, macroinitiator concentration, catalyst concentration, surfactant concentration, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP are also reported. (c) 2005 Wiley Periodicals, Inc.